Successful typical application of two-color infrared thermometer
- 2019-05-10-

I. Polysilicon production

When the production of polysilicon starts, the semiconductor silicon core is instantly broken down by high voltage in the reduction furnace. The current through the silicon core makes the silicon core reach the process requirement of 1080 ° C, and this process temperature must be used during the growth of the silicon core from φ7mm to φ180mm. Keep it constant. However, as the diameter of the silicon rod continues to increase, its corresponding impedance will continue to decrease, and the heating capacity of the silicon rod by the current will decrease. To maintain a constant silicon rod temperature of 1080 ° C, the operating current can only be increased accordingly (the current will increase from 30A at the beginning to 2800A at the end). Such a large dynamic range current change places quite high demands on production equipment and operators. In addition, the silicon rod will melt when it reaches 1420 ° C, so it is important to accurately measure the temperature of polysilicon.

Difficulties in measurement:

(1) The silicon core diameter at the beginning of production was only φ7mm, and the target was too small.

(2) When measuring the temperature of the silicon rod with a single-color infrared thermometer, the device must be installed outside the reduction furnace and aimed at the target in the furnace through a sealed window. The effect of window pollution on the transmittance results in actual measurement errors.

(3) Double-layer window glass has a large attenuation of infrared signals.

Advantages of using a two-color thermometer:

(1) The dual colorimetric temperature measurement principle is used to directly measure the true temperature of the target, and it is basically not affected by the emissivity of the material, and there is no need to compensate the emissivity.

(2) Eye sighting, you can directly see the target.

(2) Not sensitive to slight pollution of the window.

(3) It has got rid of the dependence on the relative energy of infrared and is not sensitive to signal attenuation.

Second, the vacuum sintering furnace

A vacuum sintering furnace is a furnace for protectively sintering an object to be heated in a vacuum environment. There are many heating methods, such as resistance heating, induction heating, and microwave heating. Vacuum sintering is performed under the conditions of vacuum or protective atmosphere, heating the carbide tip and various metal powder compacts to achieve sintering. During the production, substances are volatilized and water vapor will cause pollution to the light path and windows.

Advantages of using a two-color thermometer:

(1) The temperature measurement is not affected by the pollution of the light path.

(2) Not sensitive to window pollution.

Three, salt bath stove

The salt bath furnace is an industrial furnace that uses molten salt solution as a heating medium to immerse the workpiece in the salt solution (the metal electrode can be heated in the salt solution). According to the working temperature of the furnace, sodium chloride, potassium chloride, barium chloride, sodium cyanide, potassium cyanide, sodium nitrate, potassium nitrate and other salts are usually selected as the heating medium. The heating speed of the salt bath furnace is fast and the temperature is uniform. The workpiece is always heated in the salt solution, and a salt film is attached to the surface when the workpiece is out of the oven, so it can prevent the surface of the workpiece from being oxidized and decarburized. There is a certain amount of smoke during heating, which is harmful to the human body. Smoke extraction equipment should be added. Contamination of the instrument lens.

Advantages of using a two-color thermometer:

(1) The temperature measurement is not affected by smoke pollution.

(2) Slight pollution of the thermometer lens will not affect the temperature measurement.

4. Hot rolling of steel billets and strips

During the hot rolling process, the slab is heated in a heating furnace so as to be rolled after softening. If the temperature of the metal is too low, surface cracks will occur due to the hardness during subsequent rolling, and the rolling equipment will also be damaged. If the metal temperature is too high, surface cracking, melting or defects will occur during the rolling process. If the metal is heated unevenly, the steel will be deformed irregularly, resulting in poor product quality and even waste products. When measuring the temperature of the slab of the monochromatic infrared thermometer, there are effects such as scale and water vapor, among which the scale has a high emissivity and the slab has a low emissivity.

Advantages of using a two-color thermometer:

(1) There is no emissivity effect due to scale.

(2) The two-color infrared thermometer lens is slightly polluted and does not affect the temperature measurement.

After the strip is rolled into the final shape, water quenching is used to achieve the desired crystal structure and mechanical properties. If the metal cools faster, the crystal structure of the metal is finer and the hardness is higher. If cooling is slow, the metal will be relatively soft and pliable. For some steel types, such as duplex steel, it is necessary to cool the sheet to a lower temperature, and sometimes rapid cooling is required to ensure hardness. In this case, the temperature measurement during the cooling process is very important because it is an important condition for whether the product can meet the qualified characteristics. Naturally, the temperature of the strip is measured during the quenching process, and water and concentrated steam are a serious interference. In this case, the selected sensor must be able to measure through steam and water, but sensors that can measure through the water layer are not present. Therefore, measurements need to be performed without standing water.

Advantages of using a two-color thermometer:

(1) No emissivity effect caused by scale.

(2) The two-color temperature measurement technology eliminates most of the effects of water vapor.

(3) Slight contamination of the thermometer lens does not affect the temperature measurement.

In fact, countless facts have proved that, where most monochrome infrared thermometers are difficult to measure or the results are not satisfactory, you can use two-color infrared thermometers to achieve the desired results.